Prevalence, characteristics and significance of ventricular tachycardia detected by 24-hour continuous electrocardiographic recordings in the late hospital phase of acute myocardial infarction

Abstract

A 24-hour continuous electrocardiographic recording was made 11 ± 3 days after acute myocardial infarction (AMI) in 820 of the 867 participants in the Multicenter Post-Infarction Program. Ninety patients (11%) had unsustained ventricular tachycardia (VT) and 2 (0.2%) had sustained VT (more than 15 seconds). In 53 of the 92 patients (58%) with VT, only 1 episode of VT was in the recording. In 26 patients the longest episode of VT was 3 consecutive complexes (28%); in 56 patients (61%) it was 4 to 10 complexes; and in only 10 patients (11%) were there more than 10 consecutive complexes. The average rate of VT was 121 ± 34 complexes per minute (range 75 to 240). Most episodes of VT started well after the T wave. Occurrence of VT was strongly related to the frequency of ventricular premature complexes in the 24-hour recording; 46% of the patients with at least 100 ventricular premature complexes per hour had VT. The 92 patients who had VT were compared to the 728 who did not with respect to relevant clinical characteristics. Several variables were significantly (p < 0.05) more common in the VT group: age older than 60 years, previous AMI, history of angina pectoris, occurrence of VT or ventricular fibrillation in the coronary care unit, left ventricular ejection fraction less than 30%, rales greater than bibasilar in the coronary care unit, and use of antiarrhythmic drugs, digitalis or diuretics at the time of discharge from hospital. Based on Kaplan-Meier survival curves, the cumulative probability of surviving 3 years was 0.67 for patients with VT and 0.85 for patients without VT (p < 0.001). There were no statistically significant associations between individual VT characteristics and mortality. However, patients with longer runs of VT tended to have a higher mortality rate, and both patients with sustained VT died in the first month after the index infarct. VT had a strong and statistically significant association (p < 0.05) with all-cause and arrhythmic mortality independent of other risk variables that were associated with VT. Adjusted for other risk indicators, VT nearly doubled the risk of dying during an average follow-up of 31 months.